diff --git a/.github/workflows/wheels.yml b/.github/workflows/wheels.yml
index 8902601..093d2e2 100644
--- a/.github/workflows/wheels.yml
+++ b/.github/workflows/wheels.yml
@@ -48,8 +48,10 @@ jobs:
           CIBW_SKIP: "cp38-*"
           CIBW_TEST_REQUIRES: pytest pytest-asyncio
           CIBW_TEST_COMMAND: pytest {project}
-          # Only needed to make the macosx arm64 build work
-          CMAKE_OSX_ARCHITECTURES: "${{ matrix.arch == 'arm64' && 'arm64' || '' }}"
+          # Force libcapnp to build for the target arch on macOS (the runner
+          # is arm64, so without this an x86_64 wheel ends up linking against
+          # an arm64 libkj/libcapnp and failing to load at test time).
+          CMAKE_OSX_ARCHITECTURES: "${{ runner.os == 'macOS' && matrix.arch || '' }}"
 
       - uses: actions/upload-artifact@v6
         with: